1. Field of the Invention
The present invention relates to an optical blur correction apparatus which prevents the occurrence of image blur by moving a lens or an image sensor in accordance with the deviation of an optical axis caused by camera shake.
2. Description of the Related Art
Lens shift is known as one type of optical blur correction mechanism. In the lens shift type, a gyroscopic sensor and a correction lens are arranged in a lens barrel and image blur due to camera shake is canceled by driving the correction lens based on an output of the gyroscopic sensor. A movable portion on which the correction lens is mounted is loosely supported by a lens barrel body, for example by an elastic body, and the position of the movable portion is controlled within a specific range (range of motion) in a plane perpendicular to an optical axis by an electromagnetic actuator including a coil, a magnet, a yoke, and the like. The movable portion can move substantially freely within the range of motion. Therefore, due to gravity, the movable portion drops downward within the range of motion when blur correction control is in an OFF state and the center of the correction lens deviates from the optical axis.
Accordingly, a mechanical locking mechanism may be used to fix the movable portion in place by fitting a lock pin (locking member) into a lock hole formed in the movable portion. Namely, when the blur correction control is in an OFF state, the center of the correction lens is fixed on the optical axis by the locking mechanism. However, since there is play in such a mechanical locking mechanism, the correction lens can still deviate in the direction of gravity within the range of play when the blur correction control is suspended in a locked state. Accordingly, unintentional blur can occur instantaneously in a finder image or monitor image even in the locked state. To solve such a problem, US 2004/0017485 A1 discloses a system that detects the direction of gravity when the movable portion is locked and the correction lens is moved beforehand to the deviation position before the blur correction control is turned off.